Heydari, Mohammad, Zhou Xiaohu, Kin Keung Lai, Zheng Yuxi, and Lin Chen. 2019. “INVESTIGATING THE IMPACT OF CRISIS ON CORPORATE COSTS AND SALES USING ECONOMETRICS METHOD”. Proceedings of National Aviation University 81 (4):71-85. https://doi.org/10.18372/2306-1472.81.14604.